Ventricular defibrillation with myocardial electrodes in the dog, calf, pony, and pig.

The research study evaluated defibrillation effectiveness, using myocardial electrodes in various animals such as dogs, calves, ponies, and pigs to assess their suitability as models for automatic implanted defibrillator research. The findings showed variable success rates across different animals, pointing towards potential unsuitability of larger animals for implantable defibrillator research.

Research Methodology

• The study evaluated defibrillation effectiveness of 4-msec rectangular wave shocks using myocardial electrodes in four different types of animals: dogs, calves, ponies, and pigs.
• The selected animals were part of an assessment to determine their suitability as models for automatic implanted defibrillator research.
• Various electric shocks ranging from 4-A, 6-J to 8-A, 16-J were administered to the animals, and the success of defibrillation was measured.

Results and Observations

• The success rate of defibrillation in dogs varied between 44% on the lower side and as high as 93% on the higher side.
• Calves showed uniformly lower success rates, maxing at 28% with 23-A, 107-J shocks.
• Pigs revealed a relatively higher success rate (43%), more comparable to dogs, at the 12-A, 25-J shock level. However, with larger electrodes, calves managed only 63% success at the 25-A, 52-J level.
• Ponies were the least responsive to defibrillation, showing a low success rate even at a high 25-A, 100-J level with the larger electrodes.
• Globally, the research highlighted marked differences in responses between dogs and calves inconsistent with the usual closed-chest defibrillation behavior observed in both animals.

Implications and Conclusion

• The findings of the study signaled potential challenges in using larger animals such as calves and ponies as suitable models for implantable defibrillator research due to their lower and inconsistent response to defibrillation.
• At the same time, dogs and pigs emerged as somewhat more suitable models thanks to a relatively better response to different shock levels. Nonetheless, even among these species, the success rate varied considerably, pointing towards the need for further investigations into effective animal models for this research.